The present invention relates to a water treatment apparatus having meshed tubes provided with cilia and a water treatment method using the same. More particularly, the present invention relates to a water treatment apparatus including a plurality of meshed tubes made of synthetic yarn and provided with cilia and a plurality of tube stack cages containing the meshed tubes, so that biologically treated sewage and wastewater, rainwater, etc. are treated by using the tubes and cages to remove low-concentration pollutants such as soluble organic materials and suspended solids, as well as a water treatment method using the same.
As generally known in the art, pollutants contained in sewage and wastewater include high-concentration soluble organic materials and suspended solids, which are commonly removed through activated sludge (biological treatment) and sediment processes until the concentration of soluble organic materials (in terms of biological oxygen demand or BOD) and suspended solids (SS) drops below about 20 mg/L. The treated water is then discharged to streams, rivers, etc.
In the case of water from nonpoint pollution sources, such as surface runoff from rainwater, the concentration of suspended solids is high, but that of soluble organic materials is very low. This means that the water can be discharged to streams and rivers without special treatment.
There has been a worldwide consensus that removal of pollutants from sewage and wastewater suffices to prevent pollution of rivers and streams. However, such an approach has barely improved the water quality of streams and rivers. Therefore, it has recently been common to conduct further filtration after biological treatment and secondary sedimentation. It has also been mandatory to treat rainwater and remove pollutants before discharging it.
Conventional methods for removing low-concentration soluble organic materials and suspended solids include sand filtration, granulation of plastic or ceramic and its use as a carrier, and microfiltration using a synthetic membrane.
The sand filtration requires complicated underlying water collection facilities and operation systems, and occupies a large area of land, making it unpopular. Furthermore, it can only remove suspended solids (i.e. soluble organic materials are not removed).
The plastic or ceramic filtration has a problem in that, if the filter media are installed fixedly, suspended solids and soluble organic materials are removed only through pores between the media, and the resulting slime tends to clog the pores, even the channels. In an attempt to solve this problem, it has been proposed to employ movable filter media. However, collision between the media detaches microorganisms.
The microfiltration based on a synthetic membrane, which has recently been developed, relies on micropores to remove suspended solids, but it cannot remove soluble organic materials.
As mentioned above, conventional filter media have the following problem: pores between the media provide filtration space, and fluid can only flow in one direction through the pores, i.e. upward, downward, or laterally. As a result, hydraulic mixing in the reaction tank occurs in a plug flow type. This means that the load of pollutants is very high at the entrance, but gradually decreases toward the rear end, so that pores of the entrance, which is highly loaded, are easily clogged.
Therefore, it is necessary to minimize the clogging of filter media, which is the problem of conventional filter media, and to remove both suspended solids and soluble organic materials.